1. Field of the Invention
The present invention relates to a fuel injection pump assembly for distributing and supplying fuel to cylinders of an internal combustion engine such as a diesel engine.
2. Description of the Prior Art
Diesel engines for use on automobiles require that fuel combustion be uniform and fuel ignition be regular in a desired range of speeds and loads, and fuel combustion be reliable and regular at idling speeds which are about one-eighth or one-ninth of the maximum rated speed.
It is however customary to design automotive diesel engines such that air flow in combustion chambers or cylinders, the rate of fuel injection, and atomization characteristics will be balanced for smokeless fuel combustion when the engine operates at a high speed or under a maximum speed. When the engine is idling, fuel atomization is poor and air in the combustion chambers fails to get mixed well with injected fuel, with the results that fuel ignition and combustion are unstable and the fuel undergoes incomplete combustion due to a low temperature in the combustion chambers, producing black smoke and smelly exhaust gas.
A fuel injection system having a plurality of fuel injection pumps for supplying fuel respectively to engine cylinders either includes two fuel reservoirs which are selectively closed to cut off fuel supply to one group of fuel injection pumps, or has the leads of pump plungers varied respectively for the corresponding engine cylinders. When the engine operates at a low speed or under a low load, some of the engine cylinders are disabled or rendered inoperative by cutting off the fuel supply, so that an increased amount of fuel can be injected into the remaining operating engine cylinders. Fuel combustion in the engine cylinders can thus be improved to thereby reduce generation of black smoke and smelly exhaust gas for improving fuel economy and engine warm-up operation.
However, there has been known no fuel injection pump assembly for distributing a controlled amount of fuel among engine cylinders while at the same time improving fuel combustion therein for reduction of black smoke and smelly exhaust gas.